sgsnemu: Handle IPv6 SLAAC in tun iface manually

Disable IPv6 automatic SLAAC by linux kernel and handle it manually.
This allows us gaining control on local address acquisition and set
addresses and routing properly. It will also allow us to run in ping
mode without a tun iface.

Related: OS#4434

Change-Id: Iae59cf6ffb181357e10b3080a5c751bd454f4a1f

1 files changed, 103 insertions, 58 deletions

diff --git a/sgsnemu/sgsnemu.c b/sgsnemu/sgsnemu.c
index ea52da6..69879dd 100644
--- a/sgsnemu/sgsnemu.c
+++ b/sgsnemu/sgsnemu.c
@@ -58,6 +58,7 @@
 #include "../lib/ippool.h"
 #include "../lib/syserr.h"
 #include "../lib/netns.h"
+#include "../lib/icmpv6.h"
 #include "../gtp/pdp.h"
 #include "../gtp/gtp.h"
 #include "cmdline.h"
@@ -966,41 +967,6 @@ static int process_options(int argc, char **argv)
 
 }
 
-/* read a single value from a /procc file, up to 255 bytes, callee-allocated */
-static char *proc_read(const char *path)
-{
-	char *ret = NULL;
-	FILE *f;
-
-	f = fopen(path, "r");
-	if (!f)
-		return NULL;
-
-	ret = malloc(256);
-	if (!ret)
-		goto out;
-
-	if (!fgets(ret, 256, f)) {
-		free(ret);
-		ret = NULL;
-		goto out;
-	}
-
-out:
-	fclose(f);
-	return ret;
-}
-
-/* Read value of a /proc/sys/net/ipv6/conf file for given device.
- * Memory is dynamically allocated, caller must free it later. */
-static char *proc_ipv6_conf_read(const char *dev, const char *file)
-{
-	const char *fmt = "/proc/sys/net/ipv6/conf/%s/%s";
-	char path[strlen(fmt) + strlen(dev) + strlen(file)+1];
-	snprintf(path, sizeof(path), fmt, dev, file);
-	return proc_read(path);
-}
-
 /* write a single value to a /proc file */
 static int proc_write(const char *path, const char *value)
 {
@@ -1522,8 +1488,10 @@ static int create_pdp_conf(struct pdp_t *pdp, void *cbp, int cause)
 				if (in46a_is_v4(&addr[i])) {
 					struct in_addr rm;
 					rm.s_addr = 0;
-					netdev_addroute4(&rm, &addr[i].v4, &rm);
-				}
+					if (netdev_addroute4(&rm, &addr[i].v4, &rm) < 0) {
+						SYS_ERR(DSGSN, LOGL_ERROR, 0, "Failed adding default route to %s", in46a_ntoa(&addr[i]));
+					}
+				} /* else: route will be set up once we have a global link address (Router Advertisement) */
 			}
 			if (options.ipup)
 				tun_runscript(tun, options.ipup);
@@ -1532,29 +1500,21 @@ static int create_pdp_conf(struct pdp_t *pdp, void *cbp, int cause)
 		ipset(iph, &addr[i]);
 	}
 
-	/* now that ip-up has been executed, check if we are configured to
-	 * accept router advertisements */
 	if (options.createif && options.pdp_type == PDP_EUA_TYPE_v6) {
-		char *accept_ra, *forwarding;
-
-		accept_ra = proc_ipv6_conf_read(tun->devname, "accept_ra");
-		forwarding = proc_ipv6_conf_read(tun->devname, "forwarding");
-		if (!accept_ra || !forwarding)
-			printf("Could not open proc file for %s ?!?\n", tun->devname);
-		else {
-			if (!strcmp(accept_ra, "0")) {
-				printf("accept_ra=0, i.e. your tun device is not configured to accept "
-					"router advertisements; SLAAC will not succeed, please "
-					"fix your setup!\n");
-			}
-			if (!strcmp(forwarding, "1") && !strcmp(accept_ra, "1")) {
-				printf("forwarding=1 and accept_ra=1, i.e. your tun device is not "
-					"configured to accept router advertisements; SLAAC will not "
-					"succeed, please fix your setup!\n");
-			}
+		struct in6_addr *saddr6;
+		struct msgb *msg;
+		if (in46a_is_v6(&addr[0])) {
+			saddr6 = &addr[0].v6;
+		} else if (num_addr > 1 && in46a_is_v6(&addr[1])) {
+			saddr6 = &addr[1].v6;
+		} else {
+			SYS_ERR(DSGSN, LOGL_ERROR, 0, "Failed to find IPv6 EUA on IPv6 APN");
+			return EOF;	/* Not a valid IP address */
 		}
-		free(accept_ra);
-		free(forwarding);
+		SYS_ERR(DSGSN, LOGL_INFO, 0, "Sending ICMPv6 Router Soliciation to GGSN...");
+		msg = icmpv6_construct_rs(saddr6);
+		gtp_data_req(gsn, iph->pdp, msgb_data(msg), msgb_length(msg));
+		msgb_free(msg);
 	}
 
 #if defined(__linux__)
@@ -1618,8 +1578,83 @@ static int _gtp_cb_conf(int type, int cause, struct pdp_t *pdp, void *cbp)
 	}
 }
 
+static void handle_router_adv(struct ip6_hdr *ip6h, struct icmpv6_radv_hdr *ra, size_t ra_len)
+{
+	struct icmpv6_opt_hdr *opt_hdr;
+	struct icmpv6_opt_prefix *opt_prefix;
+	int rc;
+	sigset_t oldmask;
+	struct in6_addr rm;
+	char ip6strbuf[200];
+	memset(&rm, 0, sizeof(rm));
+
+	SYS_ERR(DSGSN, LOGL_INFO, 0, "Received ICMPv6 Router Advertisement");
+
+	foreach_icmpv6_opt(ra, ra_len, opt_hdr) {
+		if (opt_hdr->type == ICMPv6_OPT_TYPE_PREFIX_INFO) {
+			opt_prefix = (struct icmpv6_opt_prefix *)opt_hdr;
+			size_t prefix_len_bytes = (opt_prefix->prefix_len + 7)/8;
+			SYS_ERR(DSGSN, LOGL_INFO, 0, "Parsing OPT Prefix info (prefix_len=%u): %s",
+				opt_prefix->prefix_len,
+				osmo_hexdump((const unsigned char *)opt_prefix->prefix, prefix_len_bytes));
+			if ((options.createif) && (!options.netaddr.len)) {
+				struct in46_addr addr;
+				addr.len = 16;
+				memcpy(addr.v6.s6_addr, opt_prefix->prefix, prefix_len_bytes);
+				memset(&addr.v6.s6_addr[prefix_len_bytes], 0, 16 - prefix_len_bytes);
+				addr.v6.s6_addr[15] = 0x02;
+				SYS_ERR(DSGSN, LOGL_INFO, 0, "Adding addr %s to tun %s",
+					in46a_ntoa(&addr), tun->devname);
+
+#if defined(__linux__)
+				if ((options.netns)) {
+					if ((rc = switch_ns(netns, &oldmask)) < 0) {
+						SYS_ERR(DSGSN, LOGL_ERROR, 0,
+							"Failed to switch to netns %s: %s",
+							options.netns, strerror(-rc));
+					}
+				}
+#endif
+				rc = tun_addaddr(tun, &addr, NULL, opt_prefix->prefix_len);
+				if (rc < 0) {
+					SYS_ERR(DSGSN, LOGL_ERROR, 0, "Failed to add addr %s to tun %s",
+						in46a_ntoa(&addr), tun->devname);
+				}
+
+				struct in6_addr rm;
+				memset(&rm, 0, sizeof(rm));
+				if (netdev_addroute6(&rm, &ip6h->ip6_src, 0, tun->devname) < 0) {
+					SYS_ERR(DSGSN, LOGL_ERROR, 0, "Failed adding default route to %s", inet_ntop(AF_INET6, &ip6h->ip6_src, ip6strbuf, sizeof(ip6strbuf)));
+				}
+
+#if defined(__linux__)
+				if ((options.netns)) {
+					if ((rc = restore_ns(&oldmask)) < 0) {
+						SYS_ERR(DSGSN, LOGL_ERROR, 0,
+							"Failed to switch to original netns: %s",
+							strerror(-rc));
+					}
+				}
+#endif
+			}
+		}
+	}
+}
+
 static int encaps_tun(struct pdp_t *pdp, void *pack, unsigned len)
 {
+	struct iphdr *iph = (struct iphdr *)pack;
+	struct icmpv6_radv_hdr *ra;
+	switch (iph->version) {
+	case 6:
+		if ((ra = icmpv6_validate_router_adv(pack, len))) {
+			size_t ra_len = (uint8_t*)ra - (uint8_t*)pack;
+			handle_router_adv((struct ip6_hdr *)pack, ra, ra_len);
+			return 0;
+		}
+	break;
+	}
+
 	/*  printf("encaps_tun. Packet received: forwarding to tun\n"); */
 	return tun_encaps((struct tun_t *)pdp->ipif, pack, len);
 }
@@ -1721,6 +1756,12 @@ int main(int argc, char **argv)
 		tun_set_cb_ind(tun, cb_tun_ind);
 		if (tun->fd > maxfd)
 			maxfd = tun->fd;
+
+		if (proc_ipv6_conf_write(options.tun_dev_name, "accept_ra", "0") < 0) {
+			SYS_ERR(DSGSN, LOGL_ERROR, 0,
+				"Failed to disable IPv6 SLAAC on %s\n", options.tun_dev_name);
+			exit(1);
+		}
 	}
 
 	if ((options.createif) && (options.netaddr.len)) {
@@ -1730,6 +1771,10 @@ int main(int argc, char **argv)
 				struct in_addr rm;
 				rm.s_addr = 0;
 				netdev_addroute4(&rm, &options.netaddr.v4, &rm);
+			} else {
+				struct in6_addr rm;
+				memset(&rm, 0, sizeof(rm));
+				netdev_addroute6(&rm, &options.netaddr.v6, 0, tun->devname);
 			}
 		}
 		if (options.ipup)